Bao Wei-min

Water-Stage Forecasting in a Multitributary Tidal River Using a Bidirectional Muskingum Method

The Muskingum flow routing method has been successfully used in many hydrologic applications due to its simplicity in concept and calculation. This paper presents a bidirectional Muskingum water-stage routing model (BDMWSRM) for water-stage forecasting in a tidal river with consideration of flood and tidal influences. The BDMWSRM separates the hydrologic processes of the tidal river into upper reach flood and downstream tidal waves, respectively. Muskingum water-stage routing method was first used to calculate the propagation of the flood and tidal waves; for the case of multitributary upper reaches, a first routing-second combining approach is used and then routed streamflows are summed up by using different weight factors for two water-stages based on the water-stage threshold. All the parameters used in the model can be adjusted automatically or determined manually. The BDMWSRM was applied in the Jiaojiang River, China for evaluating the tidal effect on the streamflow in this study. The simulated strea...

Flow Updating in Real-Time Flood Forecasting Based on Runoff Correction by a Dynamic System Response Curve

AbstractIn order to improve the accuracy of real-time flood forecasting, a new accurate and efficient real-time flood forecasting error correction method based on a dynamic system response curve (DSRC) is developed. The dynamic system response curve was introduced into the flood forecasting error correction to establish the dynamic error feedback updating model tracing the source of the error. In this study, the flow concentration of the Xinanjiang (XAJ) model is generalized into a system. The physical basis of the system response curve is the flow concentration of the hydrological model. The theoretical basis of the concept is the differential of the system response function of the runoff time series. Based on the observed and calculated discharge, the calculated runoff series was corrected using least-squares estimation, and then the flow was recalculated with the corrected runoff. The Xinanjiang model was selected to calculate runoff. The method was tested in both an ideal scenario and in a real case s...

Evaluation of Runoff Responses to Land Use Changes and Land Cover Changes in the Upper Huaihe River Basin, China

Runoff changes in response to land use and land cover changes in the Huaihe River were drastic in the last few decades and are poorly understood because results from those studies are often equivocal. Hitherto, the methodology to quantify the effects of land use and land cover changes on the runoff response has been mainly the paired catchment approach, which is a blackbox, and usually restricted to small headwater basins where a control can be established. A model-based change-detection approach is developed in this study as an alternative to paired catchment methods. This approach is particularly suited to evaluating effects of land use and land cover changes on the hydrologic response in large to mesoscale watersheds in which suitable control is not possible. The Xinanjiang model was used to evaluate the newly implemented approach in the Dapoling watershed (with an area of 1,640 km2) in the upper Huaihe river basin. Three schemes were used to examine changes in the data series: (1) Calibration for a period before (or after) changes and simulations of runoff that would have been observed without land use and land cover changes (reconstruction of runoff series); (2) comparison of calibrated parameter values for periods before and after the land use and land cover change; and (3) comparison of runoffs simulated with parameter sets calibrated for periods before and after the landcover change. The results show that, since 1976, the medium-coverage and high-coverage natural forest area has decreased, and the corresponding runoff has declined by nearly 25% from 1976 to 2005 attributable to the continuous expansion of tea gardens and human development. Model parameters, for example, the evapotranspiration coefficient KC, varied considerably from 0.64 to 0.94 attributable to the land use and land cover change within the watershed. This study demonstrates that the modeling approach may be a useful alternative to the paired watershed approach for examining land use and land cover changes and their impact on the runoff.

Estimating Selected Parameters for the XAJ Model under Multicollinearity among Watershed Characteristics

Because the problem of prediction in ungauged basins (PUB) has become a central theme of hydrological research, there is a clear need to have an effective and efficient method that can help to transfer information from gauged basins to ungauged ones. Previous research relating the parameters of a hydrologic model to physical drainage basin characteristics has had limited success. Conventional regression procedures do not take into account multicollinearity among the basin characteristics, which have a great effect on the stability of regression equations. This study presents an unbiased ridge regression estimate (URR) that can provide robust regression equations in the presence of multicollinearity. The proposed method is applied to estimate parameters of the Xinanjiang model in 20 watersheds located in southeastern China. Compared with conventional estimations, such as ordinary least squares estimate and ordinary ridge regression estimate, the URR was reduced by 78% for root mean square error, 47% for va...

Evaluating Infiltration Mechanisms Using Breakthrough Curve and Mean Residence Time

Determination of infiltration mechanism is crucial for the calculation of infiltration flux in the soil which would influence the water balance computation. Two infiltration experiments with different isotopic compositions of rainfall were conducted to analyze the infiltration type by measuring isotopic concentrations (deuterium and oxygen 18) of collected outflow water samples. Models with three transfer functions were used to simulate the isotopic variation of outflows in a soil column. The model performance was evaluated with the comparison of computed and observed isotopic values of outflow. Breakthrough curve based on the isotopic composition of rainfall, initial soil water and outflow, and mean residence time estimated on the best fitting transfer function model were applied to identify the infiltration type in the soil. The results show that infiltration type determination using the comparison between estimated and observed mean residence time and breakthrough curve are similar. Furthermore, we found that soil structure and isotope measurement error affected the determination of mean residence time. Results from this study may provide a framework for describing the infiltration processes in the soil column.